Glass-ceramic as dielectric in the high-frequency range

ABSTRACT

A glass-ceramic is disclosed, this glass-ceramic includes at least the following constituents (in mol % on oxide basis): SiO 2  1-30, Al 2 O 3  0-20, B 2 O 3  0-25, TiO 2  10-70, RE 2 O 3  0-35, BaO 5-35, SiO 2 +Al 2 O 3 +B 2 O 3 &lt;25, where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part, preferably up to 10%, by Zr, Hf, Y, Nb, V, Ta. A principal phase in the glass-ceramic is BaTi 4 O.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of international patent application PCT/EP2012/073177, filed on Nov. 21, 2012 designating the U.S., which international patent application has been published in German language and claims priority from German patent application 10 2011 119 798.6, filed on Nov. 24, 2011. The entire contents of each of these priority applications being incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a glass-ceramic which can be employed as a dielectric in the high-frequency range (frequency>200 MHz), more particularly in the gigahertz range (frequency f>1 GHz).

For a series of applications in the high-frequency range, specific materials are needed which combine an extremely high relative permittivity ∈ with an extremely low dielectric loss (tan δ). In order on the one hand to allow small antenna constructions and on the other to prevent close-range detuning by the body of a user (referred to as “body loading”), particular significance attaches to dielectric charging in the case of antennas, filters, and other devices. Required for this purpose are dielectrics which have a high relative permittivity, with ∈≧15, and also a low dielectric loss (tan δ) of not more than 10⁻², preferably lower, in the high-frequency range. Furthermore, the temperature dependence of the resonance frequency τ_(f) is to be extremely low. Lastly, a material of this kind is to be able to be processed extremely simply and inexpensively in order to allow near net shapes at favorable cost.

Known in the prior art are a series of ceramic materials which are processed by sintering operations. Glass-ceramics are likewise known—cf., e.g., a BiNbO₄ system, which is disclosed in Mirsaneh et al., “Circularly Loaded Dielectric-Loaded Antennas: Current Technology and Future Challenges”, Adv. Funct. Materials 18, (2008), pp. 1-8, for application with dielectrically charged antennas for the gigahertz range. This material can be utilized for producing the three principally utilized forms of antennas: the circularly polarized DLA helix antenna (D-LQH antenna) and the square patch antenna, and also SMD antennas. For this purpose, a glass with a composition of 30 mol % Bi₂O₃, mol % Nb₂O₅, 30 mol % B₂O₃, and 10 mol % SiO₂ is first melted conventionally at 1250° C. for two hours.

This glass was poured into cylindrical molds, relaxed at 500 to 520° C., and cooled slowly to room temperature. This was then followed by crystallization at various temperatures between 600° C. and 1000° C. Specified as an optimum value for antenna applications in the case of heat treatment at 960° C. is a relative permittivity ∈ of 15, with a quality factor Q·f₀ of 15 000 GHz and a temperature coefficient of the resonance frequency τ_(f) of −80 MK⁻¹. The crystalline phase characterized in this case was substantially orthorhombic BiNbO₄.

This system, using bismuth and niobium is expensive in terms of the raw materials.

In addition there are a series of sintered ceramic materials (cf. U.S. Pat. No. 6,184,845 B1, US 2007/063902 A1). Specified therein as dielectric material for the ceramic core of a dielectrically charged D-LQH antenna is a sintered ceramic material based on zirconium titanate and, respectively, based on zirconium tin titanate, with a relative permittivity of about 36. The material is said to be produced by extrusion or pressing and subsequent sintering.

Further sintered materials are specified in the review by M. T. Sebastian et al., “Low loss dielectric materials for LTCC applications”, International Materials Reviews, Vol. 53, 2008, pp. 57-90. Although these materials are in some cases identified as “glass-ceramics”, they are in fact sintered materials, since they are produced by the sintering of a mixture of vitreous and crystalline powders.

US 2002/0037804 A1 and US 2004/0009863 A1 further disclose dielectric ceramics which are said to form diverse crystal phases, such as, for instance, CaTiO₃, SrTiO₃, Ba Ti₄O₉, La₂Ti₂O₇, Nd₂Ti₂O, Ba₂Ti₉O₂₀, Mg₂TiO₄, Mg₂SiO₄, Zn₂TiO₄, etc., which are said to be responsible for high quality factors. These as well are sintered ceramics.

Dielectrics produced by sintering have a series of disadvantages: Every sintering operation is always associated with a certain shrinkage, leading to geometrical inaccuracies and corresponding final machining. Furthermore, every sintering operation produces a certain residual porosity, which is disadvantageous in the context of metalizing of the surface. The metal penetrates the pores and raises the dielectric loss of the dielectric.

Moreover, the production of sintered materials is fundamentally relatively inconvenient and expensive.

JP 2006124201 A, moreover, discloses a lead-free glass which is said to be used for producing a dielectric for a printed circuit, having a high dielectric constant and a low electrical loss. The glass contains (in mol %): 25 to 45 SiO₂, 5 to 25 BaO, 18 to 35 TiO₂, 1 to 10 Al₂O₃, 0 to 15 B₂O₃, 0 to 15 MgO+CaO+SrO, 0 to 7 WO+ZrO₂, with ZnO<1. It is said to crystallize on heat treatment as BaTi₄O₉.

JP 2011-195440 A, which corresponds to German patent application DE 10 2010 012 524.5, discloses, in addition, a glass-ceramic comprising the following constituents (in mol % on oxide basis):

SiO₂ 5-50

Al₂O₃ 0-20

B₂O₃ 0-25

BaO 0-25

TiO₂ 10-60

RE₂O₃ 5-35

where Ba may be replaced in part by Sr, Ca, Mg, where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part by Zr, Hf, Y, Nb, V, Ta.

This glass-ceramic can be used to produce high-quality dielectrics, which are suitable in particular for high-frequency applications, such as antennas. It has nevertheless emerged as being disadvantageous here that this glass-ceramic as well is not optimized for the production of antennas, which necessitates subsequent metalizing of the surface. The residual porosity is still relatively high for this. Moreover, the raw materials costs of the known glass-ceramic with RE-Ti system and Nb—Ti systems are fairly high.

SUMMARY OF THE INVENTION

In view of this it is one object of the invention to disclose an improved material which can be employed as a dielectric for high-frequency applications.

It is a second object of the invention to disclose an improved dielectric material which having a high relative permittivity and a low dielectric loss.

It is a third object of the invention to disclose an improved dielectric material which is amenable to production and processing in an extremely simple and inexpensive way.

It is a forth object of the invention to disclose an improved dielectric material which suitable for the production of antennas.

According to one aspect of the invention these and other objects are solved by a glass-ceramic comprising at least the following constituents (in mol % on oxide basis):

SiO₂ 1-30

Al₂O₃ 0-20

B₂O₃ 0-25

TiO₂ 10-70

RE₂O₃ 0-<5

BaO 5-35

SiO₂+Al₂O₃+B₂O₃<25

wherein RE is selected from the group consisting of lanthanum, another lanthanoid, and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.

It has emerged that with a glass composition of this kind it is possible to melt homogeneous glasses which can be subsequently converted by a ceramizing treatment into a homogeneous glass-ceramic that features a high relative permittivity, a low dielectric loss, and a low temperature dependence of the resonance frequency. The material can be produced as a glass-ceramic in a simple and inexpensive way and permits near net shaping by melting processes, more particularly by pouring or, if appropriate, by pressing.

In the context of this specification, the term “glass-ceramic” refers to a material which, starting from a homogeneous glass produced by melting, is converted by a deliberate temperature treatment into a partially crystalline body, with a multiplicity of crystallites being embedded in substantially homogeneous distribution in a vitreous residual phase.

Where this specification specifies compositions by stating that certain constituents are present therein, or that they have certain constituents, these specifications shall always be understood to mean that any desired further constituents may be included therein (open composition).

In another embodiment of the invention, however, the stated compositions are also to be understood to mean that only the respectively indicated constituents are included (closed composition), apart from unavoidable impurities arising from the nature of glass manufacture. Depending on the purity of the raw materials used, such unavoidable impurities are restricted to a maximum of 1 wt %, preferably to 0.5 wt %, more preferably to 0.1 wt %, more preferably to 0.05 wt %, or even to 0.01 wt %.

Where this specification specifies compositions by stating that they consist of certain constituents, these compositions are always to be understood to mean that only the stated constituents are included therein (closed composition), albeit with the proviso that unavoidable impurities, arising from the nature of glass manufacture, may be present. Depending on the purity of the raw materials used, such unavoidable impurities are restricted to a maximum of 1 wt %, preferably to 0.5 wt %, more preferably to 0.1 wt %, more preferably to 0.05 wt %, or even to 0.01 wt %.

Where this specification specifies certain constituents in working examples by listing them, the statements are to be understood as closed compositions, albeit with the proviso that unavoidable impurities, arising from the nature of glass manufacture, may be present. Depending on the purity of the raw materials used, such unavoidable impurities are restricted to a maximum of 1 wt %, preferably to 0.5 wt %, more preferably to 0.1 wt %, more preferably to 0.05 wt %, or even to 0.01 wt %.

In an advantageous development of the invention, the glass-ceramic comprises the following constituents in mol % on oxide basis):

SiO₂ 2-20

Al₂O₃ 0-15

B₂O₃ 0-20

TiO₂ 25-55

ZrO₂ 1-15

RE₂O₃ 0-<5

BaO 10-30

SiO₂+Al₂O₃+B₂O₃≦20,

where RE is lanthanum, another lanthanoid or yttrium, and where Ti may be replaced in part, preferably up to 10% of the obligatory fraction, by Hf, Nb, V, Ta (solid solution).

In advantageous development of the invention, the glass-ceramic comprises the following constituents:

SiO₂ 2-20

Al₂O₃ 0-15

B₂O₃ 0-5

TiO₂ 40-65

ZrO₂ 5-12

RE₂O₃ 0-<5

BaO 10-30

10≦SiO₂+Al₂O₃+B₂O₃≦20,

where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part, preferably up to 10% of the obligatory fraction, by Hf, Nb, V, Ta (solid solution).

According to a further-preferred embodiment of the invention, the RE₂O₃ content is 0.1 to 4.9 mol %, more preferably 0.5 to 4.5 mol %, more preferably 0.5 to 4 mol %, very preferably 1 to 3.5 mol %, where RE is preferably only lanthanum or another lanthanoid.

The glass-ceramic may further comprise refining agents in customary amounts, which may preferably involve 0.01 to 3 mol % of a refining agent selected preferably from the group formed by Sb₂O₃ and As₂O₃.

The glass-ceramic of the invention preferably has a dielectric loss (tan δ) of not more than 10⁻², preferably of not more than 10⁻³ in the case of high-frequency applications (f>200 MHz).

Furthermore, the glass-ceramic preferably has a relative permittivity ∈ of at least 15, preferably >18, preferably in the range from 20 to 80.

The glass-ceramic of the invention is further notable preferably for a temperature dependence of the resonance frequency τ_(f) of not more than 200 ppm/K, preferably not more than 50 ppm/K, more preferably of not more than 10 ppm/k.

In further-advantageous embodiment of the invention, the glass-ceramic of the invention comprises at least one solid solution phase based on RE, Ti, Si, O, and optionally Ba, where Ba may be replaced at least in part by Sr, Ca, Mg, where RE is a lanthanoid or yttrium, and where Ti may be replaced at least in part by Zr, Hf, Y, Nb, V, Ta (solid solution).

More particularly the glass-ceramic of the invention may comprise at least one solid solution phase selected from the group formed by (BaO)_(x)(RE₂O₃)_(y)(SiO₂)_(z)(TiO₂)_(u), e.g. RE₂Ti₂O₇, RE₂Ti₂SiO₉, BaTi₄O₉ and RE₄Ti₉O₂₄, where RE is lanthanum, another lanthanoid, or yttrium, where up to 10% of Ba may be replaced by Sr, Ca, Mg, and where up to 10% of Ti may be replaced by Zr, Hf, Y, Nb, V, Ta (solid solution).

According to one preferred embodiment, the glass-ceramic comprises as predominant solid solution phase BaTi₄O₉ where Ba may be replaced in part by La, Ca, or Sr, and where Ti may be replaced in part by Zr, Hf, Y, Nb, V, Ta (solid solution).

A glass-ceramic of this kind can be produced with high quality and nevertheless very low raw materials costs, which are lower by a factor of approximately 10 to 100 than in the case of glass-ceramics with La—Ti and Nb—Ti systems.

According to one preferred embodiment, the glass-ceramic comprises as predominant solid solution phase (BaO)_(x)(RE₂O₃)_(y)(Al₂O₃)_(z)(TiO₂)_(u), more particularly Ba₄Al₂Ti₁₀O₂₇, where Ba may be replaced in part by La, Ca, or Sr, and where Ti may be replaced in part by Zr, Hf, Y, Nb, V, Ta.

With the predominant solid solution phase Ba₄Al₂Ti₁₀O₂₇, particularly good results have been found, with high stability of the precursor glass prior to ceramizing, and with very high-quality glass-ceramics, in conjunction with very low raw materials costs.

The glass-ceramic of the invention may preferably have a crystalline fraction of least 30 vol %, preferably up to 95 vol %.

The average crystallite size is preferably 10 nm to 50 μm and is situated preferably in the range from 100 nm to 1 μm.

The glass-ceramic of the invention is suitable in particular as a dielectric for a dielectric resonator, an electronic frequency filter element, or an antenna element, in the high-frequency range (f>200 MHz).

Suitable more particularly is its use as a dielectric for a cylindrical antenna element or a patch antenna element.

A dielectric of the invention having a dielectric loss of not more than 10⁻² in the high-frequency range can be produced with the following steps:

-   -   melting and homogenizing a starting glass which comprises the         following constituents (in mol % on oxide basis):

SiO₂ 1-30

Al₂O₃ 0-20

B₂O₃ 0-25

TiO₂ 10-70

RE₂O₃ 0-<5

BaO 5-35

SiO₂+Al₂O₃+B₂O₃<25

where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part, preferably up to 10% of the obligatory fraction, by Zr, Hf, Y, Nb, V, Ta;

pouring the starting glass into a desired shape;

cooling the starting glass to room temperature;

ceramizing the starting glass by a heat treatment.

Preference is given in this context to the use of a starting glass which comprises at least the following constituents (in mol % on oxide basis):

SiO₂ 2-20

Al₂O₃ 0-15

B₂O₃ 0-20

TiO₂ 25-65

ZrO₂ 1-15

RE₂O₃ 0-<5

BaO 10-30

SiO₂+Al₂O₃+B₂O₃≦20,

where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part, preferably up to 10% of the obligatory fraction, by Hf, Nb, V, Ta.

Used with further preference in this context is a starting glass which comprises at least the following constituents (in mol % on oxide basis):

SiO₂ 2-20

Al₂O₃ 0-15

B₂O₃ 0-5

TiO₂ 40-65

ZrO₂ 5-12

RE₂O₃ 0-<5

BaO 10-30

10≦SiO₂+Al₂O₃+B₂O₃≦20,

where RE is lanthanum, another lanthanoid, or yttrium, and where Ti may be replaced in part, preferably up to 10% of the obligatory fraction, by Hf, Nb, V, Ta.

The starting glass is brought preferably by a melting process into a near net shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparent from the description hereinafter of preferred working examples, with reference to the drawing. In the drawing:

FIG. 1 shows the result of a DTA of a first working example;

FIG. 2 shows the result of a DTA of a second working example;

FIG. 3 shows a compilation of the key properties of an experimental series of inventive glass-ceramics, comprising Ba₄Al₂Ti₁₀O₂₇ as predominant solid solution phase, as a function of the ceramizing temperature;

FIG. 4 shows an x-ray diffractometer analysis (XRD) and a DTA analysis of two samples comprising as predominant solid solution phase Ba₄Al₂Ti₁₀O₂₇;

FIG. 5 shows an x-ray diffractometer analysis (XRD) and a DTA analysis of a further sample with the predominant solid solution phase Ba₄Al₂Ti₁₀O₂₇ with small additions of ZnO and B₂O₃; and

FIG. 6 shows the state diagram of B₂O₃—CaO, which was added as a flux agent in eutectic composition in the case of the sample according to FIG. 5.

EXAMPLES

Assembled in table 1 are various glass compositions for a starting glass in the Ba—Ti—Zr—Si—O system, in some cases with additions of Al, B, RE.

The various glass samples of examples 1 to 7 are first of all conventionally melted and homogenized using customary starting materials; platinum crucibles, Pt/Ir crucibles, Pt/Rh crucibles, fused silica crucibles, or aluminum oxide crucibles may be used. The samples are melted first at 1350° C. for 2 hours, then refined at 1400° C. for 30 minutes, stirred and homogenized for 20 minutes with a platinum stirrer, allowed to stand for 10 minutes, and then poured off into suitable molds made of steed, graphite, aluminum oxide, or fused silica, for instance, and hence brought into a near net shape.

After cooling to room temperature, the glass is subjected to a ceramizing step.

A typical ceramizing cycle by means of an infrared furnace is as follows:

-   -   heating at 300 K/min to 1050° C.;     -   holding at 1050° C. for 7 seconds;     -   heating to 1203° C. at a heating rate of 50 K/min;     -   holding at 1200° C. for 15 minutes;     -   cooling to about 500° C. by switching off the furnace, with a         cooling rate of about 50 K/min;     -   removal of the sample from the furnace when a temperature of         about 500° C. is reached.

An alternative option is to carry out a ceramizing cycle in a conventional oven, by heat treatment at 925° C. over 0.5 to 20 hours.

Where necessary, the moldings, after having been poured, may be further finished by a grinding or polishing treatment or, in the case of the production of cylindrical moldings, may be subjected to centerless cylindrical grinding.

FIG. 1 shows a differential thermal analysis (DTA) of example 5 as per table 1. The peaks show the formation of different crystal phases, with the predominant crystal phase being BaTi₄O₉.

FIG. 2 shows a DTA of example 6 as per table 1. The peaks show the formation of crystal phases, with the peak at the lowest temperature, at 841° C. indicating the formation of BaTi₄O₉.

In the case of the glass compositions in the BaO—SiO₂—TiO₂ system as per table 1, the relevant glasses lie outside of the range in which stable glasses are likely according to the BaO—SiO₂—TiO₂ state diagram. Only by Ti→Zr, Ba→La, and Si→Al, B replacement, in other words by the use of solid solutions, in other words disorder in the crystal phase as well at the Ba and Ti site, was it possible to extend the glass formation range accordingly (stable starting glasses are of course a basic prerequisite for reproducible glass-ceramics having homogeneous properties).

The volume fraction of the crystalline phase in the case of examples 1 to 7 according to table 1 lies in the order of magnitude of about 30 to 60 vol %.

The relative permittivities ∈_(r) of samples 1 to 7 were measured, and were all greater than 15 and situated in the range from 20 to 50.

The samples are further notable for a low dielectric loss and a high quality.

Quality Q is the reciprocal of the dielectric loss (tan δ): Q=1/tan(δ).

The quality is measured by the Hakki-Coleman resonance method. In this case, the quality factor is determined as a product of quality Q and measuring frequency f₀. The measurements were conducted at about 7 to 8 GHz.

Apart from example 1, all examples had a quality factor Q·f₀ in the range of more than 1000 GHz. For example 5, a quality Q of 418 was measured at 7.547 GHz, in other words a quality factor of 3155 GHz.

The absolute value of the temperature coefficient of the resonance frequency is very low for all of the samples measured.

In the case of applications as a dielectric for antennas that are suitable in particular as mobile GPS antennas for cell phones, the frequency range is located above 200 MHz, more particularly in the range from about 800 MHz to 70 GHz. The dielectric charging of the antenna reduces the sensitivity of the antenna to detuning by the user.

Summarized in Table 2 are the compositions of a series of further inventive glasses as precursor glasses. The associated ceramizing data are given in tables 2a and 2b. The melt 39976 corresponds in its composition to the melt 39998. It is, however, a melt in a liter volume, with which ceramizing tests were run additionally, in accordance with table 2b, at different temperatures. For the glass-ceramics in question, the solid solution phase formed primarily was Ba₄Al₂Ti₁₀O₂₇; cf. the associated FIG. 4 with XRD (x-ray diffractometer) and DTA of a number of samples from table 2a. It is found that ceramizing in a conventional oven at 1000° C. to 1010° C. over 6 hours is optimal, with similar results at 1058° C. over 15 minutes.

Tables 3 and 3a compile further melts and glass-ceramics produced from them, with the associated properties.

In these cases, the melts, consisting of BaO, TiO₂, ZrO₂, SiO₂, Al₂O₃, La₂O₃, were admixed with small additions, of between 0.0125 mol % and 0.075 mol %, of ZnO and B₂O₃ in a eutectic composition. As is apparent from table 3a, even very small additions of 0.0125 mol % lead to high quality factors and very low dielectric losses.

Further precursor glasses, melted with small additions (0.0125-0.075 mol %) of CaO and B₂O₃ in the very low-melting eutectic composition of 35.5 mol % CaO and 64.5 mol % B₂O₃ (cf. FIG. 6), are summarized in table 4. The associated ceramizing conditions for the glass-ceramics produced from them, and the properties measured, are summarized in table 4a. FIG. 5 shows an XRD and a DTA of the sample 40171 (DEM-65). The peak in the DTA at about 1280° C. indicates the formation of the solid solution phase Ba₄Al₂Ti₁₀O₂₇. As is evident from the XRD, the glass-ceramic comprises predominantly the solid solution phase Ba₄Al₂Ti₁₀O₂₇.

The precursor glasses in question are stable and can be melted at low temperature in accordance with the procedure described above. The glass-ceramics produced therefrom are notable for particularly good properties. The raw materials for producing them are particularly favorable, and so they are suitable for mass production.

A compilation of the properties of the various glass-ceramics of tables 2 to 4, in which the predominant solid solution phase formed is Ba₄Al₂Ti₁₀O₂₇, is contained in FIG. 3. The quality factors are situated in the range from about 1000 GHz to about 6000 GHz, with temperature dependencies |τ_(f)| obtainable, depending on ceramizing temperature, that are lower than 100 ppm/K and can be brought to close to zero by means of optimized ceramizing conditions (ceramizing time 6 h). The relative permittivities ∈_(r) are in the range from about 25 to 33.

TABLE 1 Composition/mol % Properties No. BaO TiO₂ ZrO₂ SiO₂ Al₂O₃ B₂O₃ La₂O₃ f/GHz Q Qf/GHz d/mm h/mm ε_(r) tan δ 1 25 51 9 15 8.212 93 764 9.86 5.11 25.52 0.0106 2 25 52.5 7.5 6 9 9.1257 213 1944 10.05 4.69 22.5 0.0045 3 23 52.5 7.5 6 9 2 8.8686 182 1614 10.05 4.71 23.75 0.0053 4 25 52.5 7.5 5.5 7.5 2 9.178 193 1771 10.03 4.63 22.64 0.005 5 16.5 60 7.5 4.5 8 3.5 7.547 418 3155 10.04 4.82 31.9 0.0023 6 20.5 60 7.5 4 6 2 7.952 223 1773 10.04 4.71 29.55 0.0043 7 20.5 57.5 7.5 6.25 6.25 2 8.105 197 1597 10.04 4.72 28.35 0.0049

mol % wt % 39778 BaO 23 BaO 33.6359 TiO₂ 52.5 TiO₂ 40.0488 SiO₂ 6 ZrO₂ 7.0515 ZrO₂ 7.5 SiO₂ 4.2963 Al₂O₃ 9 Al₂O₃ 8.7523 La₂O₃ 2 La₂O₃ 6.2152 100 39779 BaO 22.5 BaO 32.6363 TiO₂ 52.5 TiO₂ 39.722 SiO₂ 6 ZrO₂ 6.994 ZrO₂ 7.5 SiO₂ 4.2613 Al₂O₃ 9 Al₂O₃ 8.6808 La₂O₃ 2.5 La₂O₃ 7.7056 100 39780 BaO 23 BaO 33.6617 TiO₂ 52.5 TiO₂ 40.0795 SiO₂ 5.85 ZrO₂ 6.8805 ZrO₂ 7.5 SiO₂ 4.2996 Al₂O₃ 9 Al₂O₃ 8.759 La₂O₃ 2 La₂O₃ 6.22 B₂O₃ 0.15 B₂O₃ 0.0997 100 39781 BaO 23.5 BaO 34.6522 TiO₂ 52.5 TiO₂ 40.3809 SiO₂ 6 ZrO₂ 7.11 ZrO₂ 7.5 SiO₂ 4.3319 Al₂O₃ 9 Al₂O₃ 8.8249 La₂O₃ 1.5 La₂O₃ 4.7001 100

TABLE 2a Melt Ceram. Tcer./ Freq./ Qf/ d/ h/ No. No. ° C. GHz Q GHz mm mm ε_(r) tan δ 39778 Glass 10.08 200 2016 9.91 4.41 20.1 0.0048 39778  26  859-6 h 10.32 160 1651.2 10.14 3.64 24.1 0.0059 39778 843 1011-6 h 7.61 297 2260.17 9.99 4.81 31.6 0.0032 39778 844 1058-6 h 7.447 689 5130.98 10 4.82 32.9 0.0013 39779 Glass 10.05 189 1899.45 9.89 4.42 20.2 0.005 39779  27  865-6 h 9.859 209 2060.53 10.24 3.64 26.9 0.0049 39779  30 1006-6 h 7.367 1151 8479.42 10.17 4.81 33.28 39779 845 1006-15 min 7.553 305 2303.67 9.99 4.82 32 0.0032 39779 846 1053-15 min 7.23 509 3680.07 9.95 4.82 34.1 0.0019 39780 Glass 10.11 202 2042.22 9.89 4.42 19.95 0.0047 39780 847  985 8.186 161 1317.946 10 4.83 27.1 0.0061 39780 891 1031 7.549 405 3057.345 10.28 4.68 32.9 0.0023 39780  31 1033 7.406 857 6346.94 10.19 4.82 32.8 39781 Glass 10.15 191 1938.65 9.9 4.42 19.75 0.005

TABLE 2B Melt No. Ceram. No. Tcryst./° C. Freq./ GHz Q Qf/GHz d/mm h/mm ε_(r) tan δ 39976 Glass 9.207 199 1832.193 10.36 5.03 19.82 0.0048 39976 DEM-40 840-6 h 8.62 193 1663.66 10.4 4.68 24.6 0.005 39976 DEM-68 875-6 h 8.048 242 1947.616 10.36 4.94 26.6 0.004 39976 DEM-69 900-6 h 8.086 227 1835.552 10.36 5.05 25.62 0.0043 39976 DEM-50 950-6 h 7.354 520 3824.08 10.25 4.95 32 0.0018 39976 DEM-51 975-6 h 7.289 595 4336.955 10.25 4.96 32.52 0.0016 39976 DEM-52 1000-6 h 7.305 807 5895.135 10.27 4.95 32.4 0.0011 39976 DEM-41 1010-6 h 7.307 804 5874.82 10.31 5.05 31.5 0.0011 39976 DE-893 1058-15 min 7.781 525 4084.5 10.33 4.68 30.4 0.0018 39778 DEM-26 859-6 h 10.32 160 1651.2 10.14 3.64 24.1 0.0059 39778 DE-843 1011-15 min 7.61 297 2260.17 9.99 4.81 31.6 0.0032 39778 DE-844 1058-15 min 7.447 689 5130.98 10 4.82 32.9 0.0013

TABLE 3 mol % wt % 40169 mol % BaO 23 98.9875 22.99713 BaO 22.99713 BaO 33.33165 TiO₂ 52.5 52.49344 TiO₂ 52.49344 TiO₂ 39.68647 ZrO₂ 7.5 7.499063 ZrO₂ 7.499063 ZrO₂ 8.734625 SiO₂ 6 5.99925 SiO₂ 5.99925 SiO₂ 3.405951 Al₂O₃ 9 8.998875 Al₂O₃ 8.998875 Al₂O₃ 8.673096 La₂O₃ 2 1.99975 La₂O₃ 1.99975 La₂O₃ 6.15899 ZnO 0.008925 ZnO 0.006866 B₂O₃ 0.003575 B₂O₃ 0.002353 ZnO 71.4 0.0125 0.008925 100 B₂O₃ 28.6 0.003575 40170 BaO 23 99.975 22.99425 BaO 22.99425 BaO 33.32857 TiO₂ 52.5 52.48688 TiO₂ 52.48688 TiO₂ 39.68281 ZrO₂ 7.5 7.498125 ZrO₂ 7.498125 ZrO₂ 8.73382 SiO₂ 6 5.9985 SiO₂ 5.9985 SiO₂ 3.405637 Al₂O₃ 9 8.99775 Al₂O₃ 8.99775 Al₂O₃ 8.672296 La₂O₃ 2 1.9995 La₂O₃ 1.9995 La₂O₃ 6.158423 ZnO 0.01785 ZnO 0.013733 B₂O₃ 0.00715 B₂O₃ 0.004706 ZnO 71.4 0.025 0.01785 100 B₂O₃ 28.6 0.00715 40171 BaO 23 99.95 22.9885 BaO 22.9885 BaO 33.32243 TiO₂ 52.5 52.47375 TiO₂ 52.47375 TiO₂ 39.67549 ZrO₂ 7.5 7.49625 ZrO₂ 7.49625 ZrO₂ 8.732209 SiO₂ 6 5.997 SiO₂ 5.997 SiO₂ 3.405009 Al₂O₃ 9 8.9955 Al₂O₃ 8.9955 Al₂O₃ 8.670696 La₂O₃ 2 1.999 La₂O₃ 1.999 La₂O₃ 6.157287 ZnO 0.0357 ZnO 0.027469 B₂O₃ 0.0143 B₂O₃ 0.009412 ZnO 71.4 0.05 0.0357 100 B₂O₃ 28.6 0.0143 40172 BaO 23 99.925 22.98275 BaO 22.98275 BaO 33.31628 TiO₂ 52.5 52.46063 TiO₂ 52.46063 TiO₂ 39.66817 ZrO₂ 7.5 7.494375 ZrO₂ 7.494375 ZrO₂ 8.730597 SiO₂ 6 5.9955 SiO₂ 5.9955 SiO₂ 3.40438 Al₂O₃ 9 8.99325 Al₂O₃ 8.99325 Al₂O₃ 8.669096 La₂O₃ 2 1.9985 La₂O₃ 1.9985 La₂O₃ 6.156151 ZnO 0.05355 ZnO 0.041206 B₂O₃ 0.02145 B₂O₃ 0.014119 ZnO 71.4 0.075 0.05355 100 B₂O₃ 28.6 0.02145

TABLE 3A Melt No. Ceram. No. Tcryst./° C. Freq./GHz Q Qf/GHz d/mm h/mm ε_(r) tan δ (39778 − 99.925) · ((0.714ZnO · 0.286B2O3) − 0.075) 40172 DEM-64 1040 7.4102 1238.17 9175.087 10.27 4.73 33.27 6.88*10−⁴ (39778 − 99.95) · ((0.714ZnO · 0.286B2O3) − 0.05) 40171 DEM-65 1040 7.4239 1196.04 8879.281 10.26 4.73 33.18 7.17*10−⁴ (39778 − 99.975) · (0.714ZnO · 0.286B2O3) − 0.025) 40170 DEM-66 1041 7.3872 1206.91 8915.686 10.24 4.72 33.64 7.15*10−⁴ (39778 − 99.9875) · (0.714ZnO · 0.286B2O3) − 0.0125) 40169 DEM-67 1041 7.3839 1233.6  9108.779 10.33 4.73 33.36 6.78*10−⁴ Ceramizing time: 6 h

TABLE 4 mol % mol % wt % 40173 BaO 23 99.9875 22.99713 BaO 22.99713 BaO 33.33217 TiO2 52.5 52.49344 TiO2 52.49344 TiO2 39.68709 ZrO2 7.5 7.499063 ZrO2 7.499063 ZrO2 8.734761 SiO2 6 5.99925 SiO2 5.99925 SiO2 3.406004 Al2O3 9 8.998875 Al2O3 8.998875 Al2O3 8.673231 La2O3 2 1.99975 La2O3 1.99975 La2O3 6.159087 B2O3 0.008063 B2O3 0.005306 CaO 0.004438 CaO 0.002352 CaO 35.5 0.0125 0.004438 100 B2O3 64.5 0.008063 40174 BaO 23 99.975 22.99425 BaO 22.99425 BaO 33.32961 TiO2 52.5 52.48688 TiO2 52.48688 TiO2 39.68405 ZrO2 7.5 7.498125 ZrO2 7.498125 ZrO2 8.734092 SiO2 6 5.9985 SiO2 5.9985 SiO2 3.405743 Al2O3 9 8.99775 Al2O3 8.99775 Al2O3 8.672567 La2O3 2 1.9995 La2O3 1.9995 La2O3 6.158615 B2O3 0.016125 B2O3 0.010613 CaO 0.008875 CaO 0.004705 CaO 35.5 0.025 0.008875 100 B2O3 64.5 0.016125 40175 BaO 23 99.95 22.9885 BaO 22.9885 BaO 33.32451 TiO2 52.5 52.47375 TiO2 52.47375 TiO2 39.67797 ZrO2 7.5 7.49625 ZrO2 7.49625 ZrO2 8.732754 SiO2 6 5.997 SiO2 5.997 SiO2 3.405221 Al2O3 9 8.9955 Al2O3 8.9955 Al2O3 8.671238 La2O3 2 1.999 La2O3 1.999 La2O3 6.157671 B2O3 0.03225 B2O3 0.021228 CaO 0.01775 CaO 0.009411 CaO 35.5 0.05 0.01775 100 B2O3 64.5 0.03225 40176 BaO 23 99.925 22.98275 BaO 22.98275 BaO 33.3194 TiO2 52.5 52.46063 TiO2 52.46063 TiO2 39.67189 ZrO2 7.5 7.494375 ZrO2 7.494375 ZrO2 8.731415 SiO2 6 5.9955 SiO2 5.9955 SiO2 3.404699 Al2O3 9 8.99325 Al2O3 8.99325 Al2O3 8.669909 La2O3 2 1.9985 La2O3 1.9985 La2O3 6.156727 B2O3 0.048375 B2O3 0.031845 CaO 0.026625 CaO 0.014118 CaO 35.5 0.075 0.026625 100 B2O3 64.5 0.048375

TABLE 4a Melt Ceram. Tcryst./ Freq./ Qf/ d/ h/ No. No. ° C. GHz Q GHz mm mm ε_(r) tan δ (39778 − 99.9875) · ((0.355CaO•0.645B2O3) − 0.075)/mol % 40176 DEM-70 864 8.155 195 1590.22 10.28 4.97 25.8 0.005  40176 DEM-74 950 7.831 282 2208.34 10.36 5.05 27.31 0.0034 40176 DEM-73 975 7.016 402 2820.43 10.36 5.07 33.9 0.0024 40176 DEM-72 1000 6.965 647 4506.355 10.37 5.07 34.37 0.0015 40178 DEM-60 1041 7.419 1223 9073.437 10.27 4.74 33.11 6.97*10⁻⁴ (39778 − 99.85) · ((0.355CaO•0.645B2O3) − 0.05)/mol % 40175 Glass 9.243 181 1672.983 10.36 5.03 19.66 0.0053 40175 DEM-61 1039 7.425 1196.62 8884.904 10.27 4.72 33.22 6.14*10⁻⁴ (39778 − 99.975) · ((0.355CaO•0.645B2O3) − 0.025)/mol % 40174 DEM-80 863 8.146 205 1669.93 10.35 5.07 25.1 0.0047 40174 DEM-79 950 7.785 292 2273.22 10.36 5.07 27.52 0.0033 40174 DEM-78 975 7.109 418 2971.562 10.35 5.06 33.13 0.0023 40174 DEM-77 1000 6.984 667 4658.328 10.35 5.07 34.25 0.001  40174 DEM-62 1041 7.408 1154.11 8549.647 10.29 4.74 33.15 7.47*10⁻⁴ (39778 − 99.9875) · ((0.355CaO•0.645B2O3) − 0.0125)/mol % 40173 Glass 9.218 185 1705.33 10.36 5.03 19.77 0.0052 40173 DEM-63 1044 7.418 1192.11 8840.888 10.3 4.73 33.14 7.15*10⁻⁴ Ceramizing time: 6 h 

The invention claimed is:
 1. A glass-ceramic comprising at least the following constituents (in mol % on oxide basis): SiO₂ 1-<25 Al₂O₃ 0-20 B₂O₃ 0-<24 TiO₂ 10-70 RE₂O₃ 0.1-<4.9 BaO 5-35 SiO₂+Al₂O₃+B₂O₃<25 wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 2. The glass-ceramic of claim 1, comprising at least the following constituents (in mol % on oxide basis): SiO₂ 2-20 Al₂O₃ 0-15 B₂O₃ 0-18 TiO₂ 25-65 ZrO₂ 1-15 RE₂O₃ 0.1-<4.9 BaO 10-30 SiO₂+Al₂O₃+B₂O₃≦20, wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 3. The glass-ceramic of claim 2, comprising at least the following constituents (in mol % on oxide basis): SiO₂ 2-20 Al₂O₃ 0-15 B₂O₃ 0-5 TiO₂ 40-65 ZrO₂ 5-12 RE₂O₃ 0.1-<4.9 BaO 10-30 10≦SiO₂+Al₂O₃+B₂O₃≦20, wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 4. The glass-ceramic of claim 1, comprising at least the following constituents (in mol % on oxide basis): SiO₂ 4-8 Al₂O₃ 7-11 B₂O₃ 0-1 TiO₂ 45-55 ZrO₂ 5-10 RE₂O₃ 0.1-<4.9 BaO 15-30 10≦SiO₂+Al₂O₃+B₂O₃≦20, wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 5. The glass-ceramic of claim 1, comprising at least the following constituents (in mol % on oxide basis): SiO₂ 4.5-7 Al₂O₃ 8-10 B₂O₃ 0-0.5 TiO₂ 48-55 ZrO₂ 6-9 RE₂O₃ 0.1-<4.9 BaO 20-26 wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 6. The glass-ceramic of claim 1, comprising at least 0.005 mol % of a melting additive.
 7. The glass-ceramic of claim 6, wherein the melting additive is a low-melting additive of a eutectic composed of glass-forming components.
 8. The glass-ceramic of claim 1, comprising 0.01 up to 3 mol % of at least one refining agent selected from the group consisting of As₂O₃ and Sb₂O₃.
 9. The glass-ceramic of claim 1, comprising a dielectric loss (tan δ) of not more than 10⁻² in the high-frequency range at a frequency f>200 MHz.
 10. The glass-ceramic of claim 1, having a relative permittivity ∈ of at least
 15. 11. The glass-ceramic of claim 1, having a resonance frequency with a certain temperature dependence, wherein an absolute value of said temperature dependence of said resonance frequency |τ_(f)| not more than 200 ppm/K.
 12. The glass-ceramic of any of claim 1, comprising at least one solid solution phase based on Ba, Ti, and O, wherein Ba may be replaced at least in part by at least one constituent selected from the group consisting of Sr, Ca, and Mg, and wherein Ti may be replaced at least in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 13. The glass-ceramic of claim 12, wherein said least one solid solution phase based on Ba, Ti, and O, further comprises at least one selected from the group consisting of Al, RE, and Si, wherein RE is selected from the group consisting of a lanthanoid and yttrium.
 14. The glass-ceramic of claim 1, comprising at least one solid solution phase of the formula (BaO)_(x)(RE₂O₃)_(y)(SiO₂)_(z)(TiO₂)_(u), wherein RE is selected from the group consisting of a lanthanoid, and yttrium, wherein x, y, and z are all positive integer numbers smaller than five, wherein up to 10% of Ba may be replaced by at least one constituent selected from the group consisting of Sr, Ca, and Mg, and wherein up to 10% of the obligatory fraction of Ti may be replaced by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta.
 15. The glass-ceramic of claim 1, comprising as predominant solid solution phase BaTi₄O₉, wherein Ba may be replaced in part by at least one constituent selected from the group consisting of La, Ca, and Sr, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Y, Nb, V, and Ta.
 16. The glass-ceramic of claim 1, comprising as predominant solid solution phase Ba₄Al₂Ti₁₀O₂₇, wherein Ba may be replaced in part by at least one constituent selected from the group consisting of La, Ca, and Sr, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Y, Nb, V, and Ta.
 17. The glass-ceramic of claim 1, having an average crystallite size of 10 nanometers to 50 micrometers.
 18. A dielectric resonator, electronic frequency filter element, or antenna element for the high-frequency range, having a dielectric comprising a glass-ceramic according to claim
 1. 19. A method of producing a dielectric having a dielectric loss of not more than 10-2 in the high-frequency range, comprising the following steps: melting and homogenizing a starting glass which comprises the following constituents (in mol % on oxide basis): SiO₂ 1-<25 Al₂O₃ 0-20 B₂O₃ 0-25 TiO₂ 10-70 RE₂O₃ 0.1-<4.9 BaO 5-35 SiO₂+Al₂O₃+B₂O₃<25 wherein RE is selected from the group consisting of a lanthanoid and yttrium, and wherein Ti may be replaced in part by at least one constituent selected from the group consisting of Zr, Hf, Nb, V, and Ta; pouring the starting glass into a desired shape; cooling the starting glass to room temperature; ceramizing the starting glass by a heat treatment.
 20. The glass-ceramic of claim 1, wherein the RE₂O₃ is present (in mol % on oxide basis) in an amount of 1 to 3.5. 